The possible head injury stems from a hit that Manziel took Aug. 11 against the Ottawa RedBlacks, when he was steamrolled at the goal line. Manziel was absent from practice both Tuesday and Wednesday, though head coach Mike Sherman insisted Tuesday that he didn’t have a concussion.

“On Tuesday morning, Johnny Manziel mentioned to our medical staff that he felt symptoms that could be associated with the prescribed medication he uses for a previously diagnosed medical condition,” the Alouettes said in a statement. “He then missed practice in order to have some blood work done. In view of the hit he received on Saturday and the potential mitigating side effects of his prescribed medication, the Alouettes medical staff has placed Manziel under the CFL concussion protocol for further observation and precautionary reasons. Manziel will be closely observed and assessed in the next few days.”

Manziel, who was acquired in a trade with the Hamilton Tiger-Cats on July 22, struggled over his first two starts with the Alouettes, completing 27 of 46 passes for 272 yards with no touchdowns and four interceptions.